We simultaneously measured the diffuse reflectance spectra and transmittance spectra of in vitro rat cerebral cortical tissue slices perfused with artificial cerebrospinal fluid (aCSF) in the wavelength range from 500 to 900 nm. An ischemia-like condition in the cortical tissue was induced by oxygen/glucose deprivation (OGD) of the aCSF. Diffuse reflectance and transmittance of the cortical slices were decreased and increased, respectively, during OGD. Spectral data of reduced scattering coefficients and absorption coefficients were estimated by the inverse Monte Carlo simulation for light transport in tissue. As with OGD, significant decrease of the reduced scattering coefficients and alteration of the absorption coefficient spectrum were observed over the measured wavelength range. The mean maximum amplitudes of change in the absorption coefficient at 520, 550, 605, and 830 nm were 0.33 ± 0.14, 0.30 ± 0.12, 0.30 ± 0.14, and -0.04 ± 0.16, respectively, whereas those in the reduced scattering coefficient at 520, 550, 605, and 830 nm were -0.37 ± 0.08, -0.38 ± 0.08, -0.38 ± 0.08, and -0.39 ± 0.08. Variations in the reduced scattering coefficients implied cell deformation mainly due to cell swelling, whereas those in the absorption spectra indicated reductions in heme aa(3) and CuA in cytochrome c oxidase and cytochrome c.